1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a blade outer air seal with cooling of the edges.
2. Description of the Related Art including information disclosed under 37 CFR 1.97 and 1.98
In a gas turbine engine, the turbine includes at least on stage of rotor blades that include blade tips that form a seal with an outer shroud of the engine. A gap or space is formed between the blade tip and the inner surface of the shroud in which hot gas leakage can flow. The outer shroud is formed of a plurality of shroud segments that together form a full 360 degree annular configuration around the rotating blades. Excess hot gas leakage flowing through this gap will decrease the turbine efficiency and lead to hot spots on the blade tip and shroud segment in which oxidation can develop and therefore shorten the life of the parts.
In the prior art of gas turbine engines, a blade outer air seal (BOAS) edge cooling is accomplished by drilling holes into the impingement cavity located at the middle of the BOAS from both of the leading edge and trailing edge of the BOAS as well as from the BOAS mate faces. FIG. 1 shows this prior art air cooled BOAS with the blade ring carrier 11, a cooling air supply hole 12, a forward isolation ring 15 and a rearward isolation ring 13, an upstream vane 16 and a downstream vane 14, a cooling air manifold or cavity 17, the shroud segment 16, an impingement plate 19 with a stiffener rib 20 and a plurality of impingement holes 21, a front impingement compartment 25 and a rear impingement compartment 26, and a TBC or thermal barrier coating 23 on the inner surface of the shroud segment 18 that forms the gap with a tip of the rotor blade 22. Cooling air supplied from the compressor flows through the cooling hole 12 and into the cavity 17, and then through the impingement holes 21 to produce impingement cooling on the backside of the shroud segment 18. The spent cooling air in the impingement compartments 25 and 26 then flows through the drilled cooling holes formed in the four edges of the shroud segment as shown in FIG. 2.